As is well known, for four corners in a room of a building such as a house, there are formed projected corners (corner portions) projected inwards with upright columns and interior member. The Japanese patent document mentioned below shows a conventional projected corner structure.
In this conventional projected corner structure, an upright column is composed of a lip angle steel member and two lip channel steel members provided so as to contact with two orthogonal surfaces of the lip angle steel member. A clearance heat insulating material is provided in the inside of the lip angle steel member so as to fill the inside of the lip angle steel member.
On the inner side of the projected corner, there are provided damp-proof sheets supported by frame members at an orthogonal state. An auxiliary upright column having a rectangular cross section is disposed between the confronting frame members crossing each other at right angles. Accordingly, the projected corner mentioned is formed so as to have a substantially rectangular cross section.
The Japanese patent document referred to is Published Japanese Patent Specification Publication No. 2001-49763.